Improving elevation resolution in phased-array inspections for NDT

The Phased Array Ultrasonic Technique (PAUT) offers great advantages over the conventional ultrasound technique (UT), particularly because of beam focusing, beam steering and electronic scanning capabilities. However, the 2D images obtained have usually low resolution in the direction perpendicular to the array elements, which limits the inspection quality of large components by mechanical scanning. This paper describes a novel approach to improve image quality in these situations, by combining three ultrasonic techniques: Phased Array with dynamic depth focusing in reception, Synthetic Aperture Focusing Technique (SAFT) and Phase Coherence Imaging (PCI). To be applied with conventional NDT arrays (1D and non-focused in elevation) a special mask to produce a wide beam in the movement direction was designed and analysed by simulation and experimentally. Then, the imaging algorithm is presented and validated by the inspection of test samples. The obtained images quality is comparable to that obtained with an equivalent matrix array, but using conventional NDT arrays and equipments, and implemented in real time.Fil: Brizuela, Jose David. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Camacho, J.. Consejo Superior de Investigaciones Científicas; EspañaFil: Cosarinsky, Guillermo Gerardo. Comisión Nacional de Energía Atómica; ArgentinaFil: Iriarte, Juan Manuel. Comisión Nacional de Energía Atómica; ArgentinaFil: Cruza, Jorge F.. Consejo Superior de Investigaciones Científicas; Españ

Experimental test of a trace formula for two-dimensional dielectric resonators

Resonance spectra of two-dimensional dielectric microwave resonators of circular and square shapes have been measured. The deduced length spectra of periodic orbits were analyzed and a trace formula for dielectric resonators recently proposed by Bogomolny et al. [Phys. Rev. E 78, 056202 (2008)] was tested. The observed deviations between the experimental length spectra and the predictions of the trace formula are attributed to a large number of missing resonances in the measured spectra. We show that by taking into account the systematics of observed and missing resonances the experimental length spectra are fully understood. In particular, a connection between the most long-lived resonances and certain periodic orbits is established experimentally.Comment: 14 pages, 12 figures, 1 tabl

Fabrication of sub-100 nm IDT SAW devices on insulating, semiconducting and conductive substrates

This work describes the electron-beam (e-beam) lithography process developed to manufacture nano interdigital transducers (IDTs) to be used in high frequency (GHz) surface acoustic wave (SAW) applications. The combination of electron-beam (e-beam) lithography and lift-off process is shown to be effective in fabricating well-defined IDT finger patterns with a line width below 100 nm with a good yield. Working with insulating piezoelectric substrates brings about e-beam deflection. It is also shown how a very thin organic anti-static layer works well in avoiding this charge accumulation during e-beam lithography on the resist layer. However, the use of this anti-static layer is not required with the insulating piezoelectric layer laying on a semiconducting substrate such as highly doped silicon. The effect of the e-beam dose on a number of different layers (of insulating, insulating on semiconducting, semiconducting, and conductive natures) is provided. Among other advantages, the use of reduced e-beam doses increases the manufacturing time. The principal aim of this work is to explain the interrelation among e-beam dose, substrate nature and IDT structure. An extensive study of the e-beam lithography of long IDT-fingers is provided, in a wide variety of electrode widths, electrode numbers and electrode pitches. It is worthy to highlight that this work shows the influence of the e-beam dose on five substrates of different conductive natur

Enhancement of photoacoustic detection of inhomogeneities in polymers

We report a series of experiments on laser pulsed photoacoustic excitationin turbid polymer samples addressed to evaluate the sound speed in the samples and the presence of inhomogeneities in the bulk. We describe a system which allows the direct measurement of the speed of the detected waves by engraving the surface of the piece under study with a fiduciary pattern of black lines. We also describe how this pattern helps to enhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon(R) samples in different situations and we show the limitations of the method.Comment: 8 pages, 7 figure

In vivo cranial bone strain and bite force in the agamid lizard Uromastyx geyri

In vivo bone strain data are the most direct evidence of deformation and strain regimes in the vertebrate cranium during feeding and can provide important insights into skull morphology. Strain data have been collected during feeding across a wide range of mammals; in contrast, in vivo cranial bone strain data have been collected from few sauropsid taxa. Here we present bone strain data recorded from the jugal of the herbivorous agamid lizard Uromastyx geyri along with simultaneously recorded bite force. Principal and shear strain magnitudes in Uromastyx geyri were lower than cranial bone strains recorded in Alligator mississippiensis, but higher than those reported from herbivorous mammals. Our results suggest that variations in principal strain orientations in the facial skeleton are largely due to differences in feeding behavior and bite location, whereas food type has little impact on strain orientations. Furthermore, mean principal strain orientations differ between male and female Uromastyx during feeding, potentially because of sexual dimorphism in skull morphology

Optimization of AlN thin layers on diamond substrates for high frequency SAW resonators

AlN/diamond heterostructures are very promising for high frequency surface acoustic wave (SAW) resonators. In their design, the thickness of the piezoelectric film is one of the key parameters. On the other hand, the film material quality and, hence, the device performance, also depend on that thickness. In this work, polished microcrystalline diamond substrates have been used to deposit AlN films by reactive sputtering, from 150 nm up to 3 μm thick. A high degree of the c-axis orientation has been obtained in all cases. SAW one port resonators at high frequency have been fabricated on these films with a proper combination of the film thickness and transducer size

Genomic variation and population structure detected by single nucleotide polymorphism arrays in Corriedale, Merino and Creole sheep.

THE AIM OF THIS STUDY WAS TO INVESTIGATE THE GENETIC DIVERSITY WITHIN AND AMONG THREE BREEDS OF SHEEP: Corriedale, Merino and Creole. Sheep from the three breeds (Merino n = 110, Corriedale n = 108 and Creole n = 10) were genotyped using the Illumina Ovine SNP50 beadchip(®). Genetic diversity was evaluated by comparing the minor allele frequency (MAF) among breeds. Population structure and genetic differentiation were assessed using STRUCTURE software, principal component analysis (PCA) and fixation index (FST). Fixed markers (MAF = 0) that were different among breeds were identified as specific breed markers. Using a subset of 18,181 single nucleotide polymorphisms (SNPs), PCA and STUCTURE analysis were able to explain population stratification within breeds. Merino and Corriedale divergent lines showed high levels of polymorphism (89.4% and 86% of polymorphic SNPs, respectively) and moderate genetic differentiation (FST = 0.08) between them. In contrast, Creole had only 69% polymorphic SNPs and showed greater genetic differentiation from the other two breeds (FST = 0.17 for both breeds). Hence, a subset of molecular markers present in the OvineSNP50 is informative enough for breed assignment and population structure analysis of commercial and Creole breeds

Estructura, fábrica magnética y emplazamiento de los granitos de Brealito y La Paya, basamento del valle Calchaquí, Salta, Argentina

Los granitoides de Brealito y La Paya son plutones de formas elípticas alargadas en dirección N-S emplazados respectivamente en las Formaciones Puncoviscana y La Paya. El estudio de la estructura interna de los plutones se ha abordado aplicando la anisotropía de la susceptibilidad magnética (ASM). El plutón de La Paya presenta un carácter paramagnético (K entre 1,9 y 6,7 x10- 5 SI) con una fábrica magnética controlada por la biotita, en cambio el plutón de Brealito muestra un carácter mixto (K entre 22 y 466 x10- 5 SI) con algunas estaciones en las que la contribución ferromagnética (originada por magnetita) es dominante. Las anisotropías totales medidas son coherentes con el carácter magmático de las muestras analizadas. Ambos plutones presentan semejanzas desde el punto de vista estructural. Son cuerpos de forma lenticular, concordantes con el encajante y buzando hacia el Oeste. La lineación magnética presenta buzamientos suaves en dirección N-S.The Brealito and La Paya granitoids are elliptical-shaped plutons with N-S elongation. They intrude into the Puncoviscana and La Paya Formations, respectively. The internal structure of these plutons has been studied by using field structures and applying the Anisotropy of the Magnetic Susceptibility (AMS). The magnetic fabric of the La Paya pluton reflects the orientation of biotite, the main paramagnetic mineral in this granite (K between 1.9 and 6.7 x10-5SI). Instead, the magnetic behavior of the Brealito granite is more complex since not only paramagnetic minerals, but also the ferromagnetic contribution (K between 22 and 466 x10-5SI) of magnetite crystals strongly control the magnetic fabric of some samples. Total anisotropy values of the magnetic fabrics are coherent with the magmatic nature of the analized samples. From the structural point of view, both plutons display similarities. These granites are lozenge-shaped bodies concordant with the host rocks. Their planar fabrics are mainly NS-trending and West dipping, and magnetic lineations plunge at low angles along the N-S direction

Pre-Columbian ring ditch construction and land use on a “chocolate forest island” in the Bolivian Amazon

We present a palaeoecological investigation of pre-Columbian land use in the savannah “forest island” landscape of north-east Bolivian Amazonia. A 5700 year sediment core from La Luna Lake, located adjacent to the La Luna forest island site, was analysed for fossil pollen and charcoal. We aimed to determine the palaeoenvironmental context of pre-Columbian occupation on the site and assess the environmental impact of land use in the forest island region. Evidence for anthropogenic burning and Zea mays L. cultivation began ~2000 cal a BP, at a time when the island was covered by savannah, under drier-than-present climatic conditions. After ~1240 cal a BP burning declined and afforestation occurred. We show that construction of the ring ditch, which encircles the island, did not involve substantial deforestation. Previous estimates of pre-Columbian population size in this region, based upon labour required for forest clearance, should therefore be reconsidered. Despite the high density of economically useful plants, such as Theobroma cacao, in the modern forest, no direct pollen evidence for agroforestry was found. However, human occupation is shown to pre-date and span forest expansion on this site, suggesting that here, and in the wider forest island region, there is no truly pre-anthropogenic ‘pristine’ forest

Zooplankton variability at four monitoring sites of the Northeast Atlantic shelves differing in latitude and trophic status

Zooplankton abundance series (1999–2013) from the coastal sites of Bilbao 35 (B35), Urdaibai 35 (U35), Plymouth L4 (L4) and Stonehaven (SH), in the Northeast Atlantic were compared to assess differences in the magnitude of seasonal, interannual and residual scales of variability, and in patterns of seasonal and interannual variation in relation to latitudinal location and trophic status. Results showed highest seasonal variability at SH consistent with its northernmost location, highest interannual variability at U35 associated to an atypical event identified in 2012 in the Bay of Biscay, and highest residual variability at U35 and B35 likely related to lower sampling frequency and higher natural and anthropogenic stress. Interannual zooplankton variations were not coherent across sites, suggesting the dominance of local influences over large scale environmental drivers. For most taxa the seasonal pattern showed coherent differences across sites, the northward delay of the annual peak being the most common feature. The between-site seasonal differences in spring–summer zooplankton taxa were related mainly to phytoplankton biomass, in turn, related to differences in latitude or anthropogenic nutrient enrichment. The northward delay in water cooling likely accounted for between-site seasonal differences in taxa that increase in the second half of the year